This invention relates to a PORTABLE FLUORESCENT LAMP AND INVERTER THEREFOR, and more particularly to a fluorescent lamp operated on high-frequency alternating current produced from battery direct current by a transistor inverter.
Despite the desirable efficiency in comparison with incandescent lamps, portability has been difficult to achieve with fluorescent lamps for a number of reasons. Direct d.c. operation of fluorescent lamps requires a relatively large ballast, and fairly high voltage for starting. Apparatus designed along such lines would thus be large and heavy and require a large number of battery cells to produce sufficient starting voltage. The designs for conventional 60-cycle a.c. fluorescent lights are likewise poorly adapted for portable use, as they generally involve inductive ballasting and relatively high voltages, as well as requiring use of an inverter, with its consequent losses.
Portable inverters for producing a.c. power from battery supplies have suffered from a number of disadvantages, especially as applied to an appliance such as a fluorescent lamp. First, the circuitry has been complex rather than simple, leading to high costs for labor and materials in their manufacture. This cost has deterred acceptance of portable fluorescent lights when compared with the less efficient but also less expensive portable incandescent lights. Another disadvantage has been the inefficiency of power conversion of many such inverters, leading to a high operating cost per lumen. This operating cost tended to reduce the advantage of generally higher efficiency of fluorescent lamps shown in non-portable applications.
The use of rechargeable cells, while dramatically decreasing operating costs, poses problems with protection of the cells both from excessive discharging and from excessive charging. Certain types of rechargeable cells can be permanently impaired by discharging them beyond a particular level, and the same is true of excessive charging of the cells, i.e., beyond a full-charge point.
Larger sizes of fluorescent tubes are commonly inserted into sockets which either require the tube to be rotated after lateral insertion, or which require the tube to be inserted longitudinally into one socket and then be allowed to spring back into the other socket. When smaller lamps are used as in the present device to close proximity to a reflector and protective shielding, neither conventional form of socket is entirely satisfactory, due to difficulties in manipulating the lamp into the socket.